Vapor generating apparatus



Filed July 15, 1965 FIQI INVENTOR. Friiz Eii'ers ATTORNEY United StatesPatent 3,324,838 VAPOR GENERATING AFPARATUS Fritz Eilers, OberhausenSterkrade, Nordrhein-Westfalen,

Germany, assignor to Babcock & Wilcox Limited, London, England, acorporation of Great Britain Filed July 15, 1965, Ser. No. 472,287Claims priority, application Germany, July 17, 1964, D 44, 3 4 Claims.(Cl. 122-510) This invention relates to vapor generating apparatus, andmore particularly to a construction thereof providing support fortubular walls separating flue gas passageways.

In modern large-scale vapor generators, sheet metal casings and tubularwalls have displaced masonry walls. The walls inside a vapor generatorare now made up of fluid-conducting tubes which are arranged side byside and joined together by welding to serve not only as walls orbaffles but also as heat exchangers which participate in the vaporgeneration process. Of principal concern is the problem of bracing adepending tubular wall when it is employed to partition adjoining flues.

A disadvantage of such a division or partition wall is that, due to itslarge dirneusions and the pressure difference between fiues, it mustwithstand large pressure forces at temperatures in the range of l300-F., all of which tends to produce excess bending of the division walland possible deterioration of the lateral wall-labyrinth packings. Theproblem is further complicated by the requirement that any supportingstructure for the division wall should not block the tube lanes so as tointerfere with the effective operation of soot blowers employed forremoving accumulations of soot and sintered particles from the tubesurfaces.

Thus, the principal object of the present invention is to provide asimple, economical, and effective means for supporting or bracing suchtubular division walls under the conditions set forth.

According to the present invention, the parallel tubes comprising theheat exchangers in the downstream flue are arranged normal to thepartition or division wall to be braced. Groups of these tubes areconnected together by rigid transverse structure, to be described, sothat one or more of them will not fail due to buckling as a result ofaxial or endwise compression when bracing the division wall against therear wall, or other suitable bearing surface. A slidable connection withthe transverse structure permits each of the grouped tubes to undergolongitudinal thermal expansion independent of the transverse connectingstructure. Likewise, the division wall is not rigidly connected to thebracing structure, with the result that it has freedom to undergoexpansion and contraction over its entire width and height.

It is a feature of the present invention that bracing structure for adivision wall can be provided at a very low cost and with a very smallamount of additional material, since existing heat exchanger tubes forma major part of the bracing structure. This has the further advantage ofconsuming very little additional space, with the result that the tubelanes are left clear for effective operation of the soot blowers and theflow of flue gas.

The various objects, features, and advantages of the invention willappear more fully from the detailed description which follows, taken inconnection with the accompanying drawings forming a part of the presentinvention and in which:

FIG. 1 is a schematic illustration of vapor generating apparatusembodying the invention;

FIG. 2 is an enlarged sectional view of a fragment of the apparatus ofFIG. 1, taken from the downstream or third flue and showing thestructural support for the division wall in detail; and

FIG. 3 is a transverse sectional view through the supporting structureof the present invention.

The invention, as shown in the drawings, with particular reference toFIG. 1, is applied to a vapor generating apparatus including a fuelfiring component, such as a cyclone furnace 9, and also a flue gaspassageway. The latter conducts flue gas in the direction of the arrowsin FIG. 1 and comprises a first flue or furnace chamber 10 leading to anopen gas pass or second flue 11, and then to a convection pass or thirdflue 12. The flues 11 and 12 extend vertically and are separated fromeach other by a depending, upright partition or division wall 13.Preferably, the division wall 13 is formed of upright, heat transfertubes arranged side by side and joined together by welding to close thespaces between them and provide a rigid structure. Also, there aretubulous walls made up of heat transfer tubes lining the flues toprovide radiation heating surfaces.

The third or downstream flue 12 contains a number of heat exchangers 14,i.e., superheaters, intermediate superheaters, etc. These heatexchangers 14 are disposed between the division wall 13 and a rear wall15 to provide contact heating surfaces within the flue 12 for generatingsteam by convection heating.

There is usually a pressure difference between the second flue 11 andthe third fine 12, with the greater pressure being in the second flue11. Consequently, a pressure force is applied to the division wall 13 inthe direction of the rear wall 15, tending to impose large bendingforces on the tubes and welded joints of the wall 13 in a region wherethe temperature of the flue gas is about 1300 F.

The present invention employs, from the heat exchangers 14, selectedbanks or groups of long slender heat exchanger tubes 21 extendingbetween the division wall 13 and the rear wall 15, at an attitude normalthereto, for bracing the division wall 13 against the rear wall 15 tothereby provide distributed resistance to the applied pressure forces,since the selected tubes 21 are at spaced locations on the Wall 13.

Referring now especially to FIGS. 2 and 3, the bracing structureemploying the heat exchanger tubes 21, as proposed by the invention,will now be described in detail. It will be noted that there is only asmall clearance, amounting to a fraction of an inch, between the ends ofthe heat exchanger tubes 21 and the walls 13 and 15. As shown in FIG. 3,several tubes 21, preferably three or more, are connected together inspaced relationship by connecting members 16 and upright spacers 18 offlat steel which are welded to tube shackles or collars 17, as shown,are for the purpose of making the tubes so connected rigidly resistantto bending when placed in endWise compression.

A greater number than three tubes may be connected together, for examplefive, as is also shown in FIG. 3. Only tubes from adjoining rows shouldbe connected together so that the temperature difference between tubesin a given group will be minimal. It is preferred that the shackles 17be fitted to their respective tubes with sufficient looseness to permitlongitudinal thermal expansion or differential movement of the tubes,for example, due to changes and differences in temperature between tubesin a group, while simultaneously preventing lateral outward bending.This provision is better than rigidly joining tubes together in a groupby welding directly to the tube surfaces, since such construction couldimpose high stresses on the weld in the event of differentiallongitudinal movement of adjoining tubes.

With a pressure force applied to the division wall 13 in the directionof the rear or hearing wall 15, hearing members 19 comprising channelmembers and/or bearing plates extending across the width of the flue 12are interposed between each of the walls 13 and 15 and the ends of thetubes 21 to transmit the pressure force from division wall 13, throughthe members 19 at one end of the tubs 21, through the tubes 21 and themembers 19 at the other end thereof, to the rear wall 15. Also, flatiron pieces 20 are inserted between nested neighboring tubes 21 at thelaterally extending turns or return bends in the 'tubebank, at both endsof the tube bank to prevent unequal deflection at the tube turns whichwould result in an unequal distribution of the forces applied to thetube bank by the division wall 13. Clamps can be used instead of theflat pieces with equal effect. And, with the bearing members 19 and theflat iron pieces 20 unattached to the walls 13 and 15, the division wall13 and the rear wall 15 are free to undergo thermal expansion withoutrestraint.

With the present arrangement, pressure forces from the division wall 13are distributed and transmitted to the tubes 21 in the tube bank so asto place them in endwise compression, while the connecting pieces 16,spacers 18 and shackles 17 help to prevent buckling of the tubes 21. Agroup of slender tubes rigidly shackled together with elongated shackles17 at spaced locations along their length can withstand a greateraggregate endwise compressive load without buckling than if the sametubes were completely free of attachment from one another, and theresulting structure has improved dimensional stability. If the load fromthe wall 13 is unevenly distributed on the tubes 21 the more highlycompressed tubes will be braced against buckling by the transverseconnection to the other tubes in the group; and in this way bucklingforces are distributed to all tubes in the group.

While in accordance with the provisions of the statutes there isillustrated and described herein a specific embodiment of the invention,those skilled in the art will understand that changes may be made in theform of the invention covered by the claims, and that certain featuresof the invention may sometimes be used to advantage without acorresponding use of the other features.

What is claimed is:

1. In vapor generating apparatus, the combination with first and secondflue gas passageways,

a first wall providing a partition between said passageways,

a second wall in mutually facing relationship with said first wall onopposite sides of said second passageway, and

a plurality of elongated, fluid conducting tubes in said secondpassageway and extending substantially normal to said walls and thencelaterally at their ends to provide nested return bends with spacestherebetween,

of means for bracing said first wall against deflection toward saidsecond wall, comprising:

rigid members between the endmost return bends of said tubes and saidwalls and in the spaces between adjacent return bends for transmittingdeflection forces on said first wall longitudinally through said tubesto said second wall, and

means providing transverse structural rigidity to groups of said tubescomprising rigid elements connected between adjacent tubes of said groupintermediate the ends thereof.

2. Vapor generating apparatus comprising:

a furnace chamber,

first and second passageways communicating with said furnace chamber,

an upright, depending partition wall between said passagewaysconstructed of heat transfer elements,

an upright bearing surface mutually facing said partition wall acrosssaid second passageway,

a tube bank in said second passageway comprising a multiplicity ofelongated heat transfer tubes arranged means applying a pressure forceto said partition wall in the direction of said bearing surface.

means including rigid members interposed between adjacent return bendsand also interposed between said wall and the return bend at one end ofsaid tube bank and between the return bend at the other end of said tubebank and said bearing surface for transmitting the pressure force onsaid partition wall through said tubes to said bearing surface wherebysaid tubes are placed in endwise compression,

shackles for the respective tubes mounted thereon and movablelongitudinally thereof, and

rigid elements extending transversely between adjacent shackles andjoined thereto to provide transverse rigidity to said group of tubes forresisting buckling when subjected to compressive loading.

3. Vapor generating apparatus comprising:

a furnace including a furnace chamber and a fuel firing component; wallstructure defining vertically extending first and second passagewayscommunicating with said furnace chamber and including an upright,depending partition Wall between said passageways and an upright bearingwall mutually facing said partition wall across said second passageway;

heat exchangers in said second passageway including a tube bankcomprising a multiplicity of slender, fluid conducting tubes arrangednormal to said partition wall and thence laterally at their ends toprovide nested return bends with spaces therebetween; means fordirecting flue gas from said furnace chamber first through said firstpassageway and then through said second passageway whereby a greater gaspressure exists in said first passageway than said second passageway anda pressure force is applied to said partition wall in the direction ofsaid bearing wall;

means including rigid members between adjacent return bends and alsobetween said walls and the endmost return bends of said tube bank fortransmitting the pressure force on said partition wall through saidtubes to said bearing wall whereby said tubes are placed in endwisecompression;

and bracing structure for resisting buckling of said tubes comprisingmetal annuli on said tubes slidably fitted thereto, and

rigid metal connectors extending transversely between annuli associatedin a group of said tubes and joined thereto to provide a rigidtransverse connection between tubes in said group;

the construction and arrangement being such that when an endwisecompressive load is applied to said tubes buckling is resisted by saidtubes as a group.

4. Vapor generating apparatus according to claim 3 wherein said fluidconducting tubes of said tube bank are free of attachment to saidpartition wall so that the latter is free to expand or contract over itswidth and height relative to said tubes.

References Cited UNITED STATES PATENTS 1,894,692 l/l933 Kerr et al.122-510 X 2,345,257 3/1944 Hensel et al. 122-510 2,714,877 8/1955 Andrew122-510 X 3,055,348 9/196'2 Brash l22.51O 3,055,349 9/1962 Hamilton etal l225l0 CHARLES J. MYHRE, Primary Examiner.

1. IN VAPOR GENERATING APPARATUS, THE COMBINATION WITH FIRST AND SECONDFLUE GAS PASSAGEWAYS, A FIRST WALL PROVIDING A PARTITION BETWEEN SAIDPASSAGEWAYS, A SECOND WALL IN MUTUALLY FACING RELATIONSHIP WITH SAIDFIRST WALL ON OPPOSITE SIDES OF SAID SECOND PASSAGEWAY, AND A PLURALITYOF ELONGATED, FLUID CONDUCTING TUBES IN SAID SECOND PASSAGEWAY ANDEXTENDING SUBSTANTIALLY NORMAL TO SAID WALLS AND THENCE LATERALLY ATTHEIR ENDS TO PROVIDE NESTED RETURN BENDS WITH SPACED THEREBETWEEN, OFMEANS FOR BRACING SAID FIRST WAL AGAINST DEFLECTION TOWARD SAID SECONDWALL, COMPRISING: RIGID MEMBERS BETWEEN THE ENDMOST RETURN BENDS OF SAIDTUBES AND SAID WALLS AND IN THE SPACED BETWEEN ADJACENT RETURN BENDS FORTRANSMITTING DEFLECTION FORCES ON SAID FIRST WALL LONGITUDINALLY THROUGHSAID TUBES TO SAID SECOND WALL, AND MEANS PROVIDING TRANSVERSESTRUCTURAL RIDIGITY TO GROUPS OF SAID TUBES COMPRISING RIGID ELEMENTSCONNECTED BETWEEN ADJACENT TUBES OF SAID GROUP INTERMEDIATE THE ENDSTHEREOF.